Quadrax to Twinax conversion apparatus and method

ABSTRACT

A Quadrax to Twinax conversion apparatus includes stacked trace layers of transmission line with a ground plane between the trace layers. Embodiments include trace layers of stripline or microstrip. Orthogonal plated through holes include a diagonal pair of through holes in electrical contact with traces on one of the trace layers and another diagonal pair of through holes in electrical contact with another trace layer. Contact pins extend through these orthogonal plated through holes with one pair of pins making electrical contact with one trace layer and the other pair of pins making electrical contact with another trace layer. The conversion apparatus electrically connects Twinax cables to respectively different trace layers without crossing over or disturbing the relative positions of the Quadrax diagonal pairs for very efficient high-speed data transfer from four wire Quadrax to two wire Twinax cables.

[0001] This application is a continuation of U.S. application Ser. No.10/096,087, filed Mar. 11, 2002 entitled “QUADRAX TO TWINAX CONVERSIONAPPARATUS AND METHOD” and claims the benefit of U.S. ProvisionalApplication No. 60/276,263 filed Mar. 14, 2001 entitled “QUADRAX TOTWINAX CONVERSION APPARATUS AND METHOD”, the entire contents of which isexpressly incorporated by reference.

FIELD OF THE INVENTION

[0002] This invention relates to high-speed data transference andparticularly to conversion from four wire (Quadrax) to two wire(Twinax).

SUMMARY OF THE INVENTION

[0003] High speed data transference requires transmission systems thatminimize reflections. This is achieved through controlled characteristicimpedance from source to load. In conventional microwave systems, thisis accomplished with waveguide or coaxial transmission lines. However,with current high-speed data transfer, such as fiber channel, the sourceand load differential impedances are usually high and of the order of100 to 150 ohms. Achieving these high impedances in coaxial transmissionlines is size prohibitive. A more efficient transmission line forhigh-speed data transfer is Twinax wherein the signals are carriedbetween a pair of conductors.

[0004] An even more efficient transmission line is four-channel Quadrax,wherein four wires are carried within a single enclosure. However, asdescribed below, significant problems arise when the four channels mustbe physically separated.

[0005] The preferred embodiment of the present invention provides asolution to this problem and utilizes a novel combination of stackedstripline or microstrip and contact pins extending into the through-holeplated openings to locate a common ground plane between two trace layersto couple to two wire (Twinax) conductor without disturbing the relativepositions of the diagonal pairs of the four wire (Quadrax) conductor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1(A) illustrates a single conductor coaxial transmission linein cross-section;

[0007]FIG. 1(B) illustrates a two conductor (Twinax) transmission linein cross-section;

[0008]FIG. 1(C) illustrates a four conductor (Quadrax) transmission linein cross-section;

[0009]FIG. 2 illustrates, in partial cross-section, the externalconfiguration of one embodiment of the invention;

[0010] FIGS. 3(A) and 3(B) respectively illustrate, in cross-section andin substantial enlargement, the stripline and the microstriptransmission line configurations;

[0011]FIG. 4 is an enlarged perspective view of a four layer striplineused in the preferred embodiment of this invention;

[0012]FIG. 5 is a horizontal elevational view of the stripline of FIG.4;

[0013]FIG. 6 illustrates a top plan view of the ground plane plans andtrace layers of the stripline of FIG. 4;

[0014]FIG. 7 illustrates the use of multiple layers of stripline board;

[0015]FIG. 8 illustrates a connector utilizing the multiple layers ofFIG. 7;

[0016]FIG. 9 is an elevational end view of another embodiment of theinvention in which the Quadrax cable entry is bolted to a panel;

[0017]FIG. 10 is a perspective view of the Quadrax to Twinax connectorincluding a connector for the Quadrax cable;

[0018]FIG. 11 is another perspective view of the apparatus of FIG. 10with the connector body removed to illustrate the internal connectorpins; and

[0019]FIG. 12 is an enlarged view of the connector of FIGS. 10 and 11with the layer 2 of FIGS. 5 and 6 exposed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] Currently, high-speed data transference requires transmissionsystems that minimize reflections. This is achieved through controlledcharacteristic impedance from source to load. In microwave systems, thisis accomplished with waveguide or coaxial transmission lines. In bothcases, the line geometry is the determining factor along with dielectricand conductor materials. Steps, bends, protrusions etc. will invariablycause reflections with consequent loss of transmission efficiency(insertion loss) and sending-end disturbance. In 2-wiredifferential-mode transmissions this is acceptable at lower data rates.When data rates become higher, such as fiber channel (into microwavefrequencies), the line characteristic impedances become much morecritical.

[0021] In fiber channel systems the source and load differentialimpedances are usually high (100-150 Ω). Achieving these high impedancesin a coaxial transmission line 20 (FIG. 1(A)) is size prohibitive. As aresult, a line configuration such as Twinax 25 (FIG. 1(B)) wherein thesignals are carried between a pair of conductors (usually round)critically spaced from each other and surrounded by a conductiveenclosure. In this “differential line,” high impedances are easilyobtained since the mutual capacitance between the conductors isminimized.

[0022] A more efficient development for fiber channel transmission iscalled Quadrax 30 (FIG. 1(C)), having a single enclosure enclosing fourwires 35, 36, 37, and 38. In Quadrax, a pair of conductors forms aTwinax differential pair. These respective pairs 35, 36 and 37, 38 mustbe diagonal because the paired conductor electric fields are mutuallyperpendicular and will therefore not couple. This condition eliminatescross talk, maintaining channel isolation.

[0023] Quadrax rather than Twinax is advantageously employed for longerline runs. However, a significant problem arises in the prior art whenthe two orthogonal channels of the Quadrax are physically separated intotwo separate pairs of Twinax. In the prior art, the pairs of the Quadrax30 cross over when converted to Twinax resulting in impedancedisturbance and reflections with some cross talk. At low frequencies ordata rates, this is somewhat manageable, however, when data ratesapproach microwave frequencies, the resulting system degradation becomesunacceptable.

[0024] The preferred embodiments of this invention utilize a novelcombination of transmission line configuration(s) of stripline 40 ormicrostrip 41 (FIG. 3), to solve the problem of converting Quadrax toTwinax. Moreover, the embodiment described advantageously enables theconversion to be performed in a connector apparatus. As shown in FIG. 2,two Twinax conductors 25 a and 25 b are connected to one end 35 of aconnector apparatus and the Quadrax cable 30 is connected to the otherend 36 of a mating connector apparatus. Either stripline or microstripconfigurations may be used, however, stripline will be described below.

[0025] Strip transmission line is a method of transmitting RF signals ina controlled impedance environment. The signal bearing line is a metalstrip 42 a, 42 b between two ground planes 43 a, 43 d and separated bydielectric circuit boards 44 a, 44 b (see FIG. 3). The conductive metalstrips 42 a, 42 b are typically formed on the dielectric boards 44 byselective removal by chemical etching of the metal to leave the residualstrips 42.

[0026] The initial construction of one embodiment of the invention isbest illustrated in FIGS. 4, 5, 6 and 8 in which a multi-level stackcomprises locating a first trace layer on level 2 between groundplanes 1and 3 and a second trace layer on level 4 between ground planes 3 and 5.The first traces 60, 61 on trace level 2 terminate at pad openings 65,66 whereas a second set of traces 70, 71 on trace level 4 terminate atpad openings 75, 76. The two conductors of a first Twinax line 25 aconnect to respective ends of 80, 81 of traces 60, 61. The twinconductors of a second Twinax line 25 b connect to respective ends 85,86 of traces 70, 71. The differential pair of conductors are soldered,or otherwise affixed to the surface pads on levels 2 and 4 shown inFIGS. 5 and 6.

[0027] The four conductors of the Quadrax cable 30 respectivelyelectrically connect to one of the strips 60, 61, 70, 77 by contact pins90, 91, 92, 93. These contact pins are best shown in FIG. 8, whichillustrates in cross section a connector adapted to connect to a pair ofside-by-side Quadrax cables 30 a and 30 b and in FIG. 12, whichillustrates a connector adapted to connect to a single Quadrax cable.Contact pins 90, 91, 92, 93 couple straight onto the stripline traceswithout crossing over or disturbing the relative positions of theselected diagonal pairs. This is accomplished by a series of platedthrough holes through the multi-level stack and is best shown in FIGS. 4and 5. The diagonal pairs from the Quadrax interface are attached to thepad openings on their assigned traces, while merely passing through thethrough-holes in the other board having the traces and pads belonging tothe other diagonal pair. Thus, referring to FIGS. 8 and 12, one pair ofpins 90, 91 are in electrical contact with through-hole pad openings,such as pads 65, 66 of layer 2 (shown in FIG. 6), but do not contact thetraces on layer 4. As noted above, these through-hole openings 65, 66are respectively in contact with traces 60, 61. The other pair of pins92, 93 (best shown in FIG. 8) are in electrical contact withthrough-hole pad openings of layer 4 (examples being pads 75, 76 shownin FIG. 6), but merely pass through layer 2 without contacting thetraces on this layer 2. This maintains the impedance relativelyconsistent and therefore not frequency sensitive.

[0028] Referring to FIGS. 2 and 8, when connector body 36 engagesconnector body 35, the pins 90, 91, 92, 93 of connector 35 are engagedby corresponding conductors in connector 36 which in turn are connectedto the internal conductors of one or more Quadrax cables 30.

[0029] Referring to FIGS. 4, 5 and 6, a common ground plane (3) islocated between the two trace layers (2 and 4). As a result, the tracesignal pairs 60, 61 and 70, 71 will be isolated with each signal pair inthe controlled impedance of effectively two separate transmissionsystems. As described above and shown in FIGS. 6 and 8, these separatedpairs run to respective surface pads 80, 81 and 85, 86 and selectedthrough plated-through holes connect to the assigned embedded traces.

[0030] The configuration described and shown in FIGS. 4, 5, and 6 can beduplicated on a multiplicity of regions on a single multi-layeredstripline board or several boards (as shown in FIG. 7).

[0031] The embodiment shown in FIGS. 2 and 8 includes a connector havingsections 35, 36. However, an embodiment of the invention can be alsoconfigured to attach directly to a panel with a header as shown in FIG.9, wherein the Quadrax cable entry 100 is simply bolted to a panel 105.

[0032] The 90° exit of the separate differential Twinax cables 25 a and25 b shown in FIGS. 8, 10 and 11 are examples of the invention. In otherembodiments, the cables 25 a and 25 b can exit at any convenient angleincluding straight out the back, as shown in FIG. 9.

[0033]FIGS. 11 and 12 show the assembly of the connector of FIG. 10 withthe connector shell removed exposing the stripline assembly.

[0034] The dimensions and material properties of the boards shown inFIGS. 5 and 6 are determined by the applicable well known equations.When the preferred conditions are achieved, the transmitted signal(source) is very efficiently delivered to its destination (load).

[0035] The equations for stripline are included in Appendix A(1) andA(2). The specifications for exemplary dielectric board 44 are providedby Appendix B. Manufacturing information of an exemplary embodiment areshown in Drawing No. 145-0097-000 (Appendices C1, C2 and C3).

[0036] Although this invention has been described in terms of certainpreferred embodiments, other embodiments that are apparent to those ofordinary skill in the art, including embodiments which do not provideall of the benefits and features set forth herein, are also within thescope of this invention.

What is claimed is:
 1. A conversion apparatus for connecting from a highspeed data cable having two orthogonal pairs of conductors comprising:two or more stacked dielectric boards supporting electrical traces, aground plane between said stacked boards; plated through holes in saidboards respectively in contact with said traces; first conductorsconnected to plated through holes on one of said boards; secondconductors connected to plated through holes on another of said boards;electrical connections between said first conductors and one of said twoorthogonal conductors; electrical connectors between said secondconductors and the other of said two orthogonal connectors; a first highspeed data cable having a single pair of conductors; a second high speeddata cable having a single pair of conductors; electrical connectionsbetween said traces on one of said dielectric boards and the conductorpair of said first high speed data cable; and electrical connectionsbetween said traces on another of said dielectric boards and theconductor pair of said second high speed data cable.
 2. The method oftransference of high speed data between Quadrax cable and Twinax cable,comprising: forming traces ending in plated through holes on a firstdielectric board; forming traces ending in plated through holes on asecond dielectric board; stacking said boards between ground planes;connecting conductors to traces on said first board through said throughholes so that said conductors do not electrically connect to said traceson said second board; connecting conductors to traces on said secondboard through said through holes so that said conductors do notelectrically connect to said traces on said first board; attaching theconductors connected to traces on said first dielectric board to a firstorthogonal pair of the Quadrax cable; attaching the conductors connectedto traces on said second dielectric board to a second orthogonal pair ofthe Quadrax cable; connecting said traces on said first dielectric boardto a first Twinax cable; and connecting said traces on said seconddielectric board to a second Twinax cable.
 3. A conversion apparatus forconnecting from a high speed data cable having two diagonal pairs ofconductors comprising: physically displaced first and second circuits; aground plane between said circuits; and conductors from said first andsecond circuits respectively to said orthogonal pairs of conductorswithout disturbing the relative positions of said diagonal pairs ofconductors.
 4. A connector for efficiently connecting Quadrax and Twinaxcables comprising: a multi-level stack of boards including first andsecond trace layers and a ground plane between said first and secondtrace layers; said trace layers including four substantially diagonalthrough holes with said first trace layer connected to one set ofdiagonal holes and said second trace layer connected to the other set ofdiagonal holes; said first trace layer adapted to connect to a firstTwinax cable; said second trace layer adapted to connect to a secondTwinax cable; one set of diagonal through holes adapted to connect toone set of diagonal wires of said Quadrax cable; and the other set ofdiagonal through holes adapted to connect to the remaining set ofdiagonal wires of said Quadrax cable.
 5. The connector of claim 4,wherein said trace layers are transmission lines.
 6. The connector ofclaim 5, wherein said trace layers are strip line configurations.
 7. Theconnector of claim 5, wherein said trace layers are microstripconfigurations.
 8. The connector of claim 4, having at least two sets offour substantially diagonal through holes to accommodate at least twoQuadrax cables.
 9. The connector of claim 4, wherein respective pairs ofdiagonal electrical connector pins passing through said through-holeselectrically connect to respective trace layers for connecting theorthogonal pairs of conductors of said Quadrax to respective tracelayers without disturbing the relative positions of said orthogonalconductors.
 10. The connector of claim 4, wherein said sets of diagonalthrough holes are in substantial alignment with the diagonal wires ofsaid Quadrax cable.